<h2>DESCRIPTION</h2>

<em>v.net.components</em> computes the weakly and strongly connected 
components in a network.

<h2>NOTES</h2>
Two nodes, <em>u</em> and <em>v</em> are in the same strongly connected 
component if there are directed paths from <em>u</em> to <em>v</em> and 
from <em>v</em> to <em>u</em>. The nodes are in the same weakly 
connected component if, ignoring edge directions, there is a path 
between them.
<p>
The type of components is specified by <b>method</b> parameter. 
<em>v.net.components</em> creates a table and links it to layer 1. This 
table contains only two integer columns: <em>cat</em> and 
<em>comp</em>. If a point or both endpoints of a line belong to the 
same component then the point/line is written to the output map and 
appropriate information is stored in the table. If <b>-a</b> flag is 
set then new points are added on the nodes without points. These points 
have category numbers larger than any category used in the input map.
<p>
One-way roads can be defined by assigning a cost of -1 to the 
appropriate cost column (<b>arc_column</b> or 
<b>arc_backward_column</b>). This affects only strongly connected 
components. Network nodes can be closed by assigning a cost of -1 to 
the node cost column. All nodes with a cost &lt; 0 can not be traversed 
and are end points, while all nodes with a cost &ge; 0 can be traversed. 
This affects both weakly and strongly connected components.

<h2>EXAMPLES</h2>

Any road network should form a single strongly connected component. 
Otherwise, it is impossible to travel between some places.
<div class="code"><pre>
v.net.components input=roads output=roads_components method=strong
</pre></div>

<h2>SEE ALSO</h2>

<em>
<a href="v.net.html">v.net</a>,
<a href="v.category.html">v.category</a>,
</em>

<h2>AUTHORS</h2>

Daniel Bundala, Google Summer of Code 2009, Student<br>
Wolf Bergenheim, Mentor<br>
Markus Metz

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